Iterating over list of list of object - c++

Question

I want to iterate over a list of list of Object,
list<list<Point>> gnuPoints;
this is a static list which accepts list from various classes like circle and polygon all of which classes pushes multiple objects i.e Point(x,y) to the list
while (angle != 360)
{
double x = m_radius*cos(angle);
double y = m_radius*sin(angle);
angle += 30;
circlePoint.push_back(Point(x, y));
}
similarly goes with Polygon and line shapes
polygonPoint.push_back(Point(x,y));
linePoint.Push_back(point(x,y));
then these lists are pushed in gnuPoint(list< list< Point> >).
gnuPoints.push_back(circlePoints);
gnuPoints.push_back(polygonPoints);
gnuPoints.push_back(linePoints);
now i want to write all these x,y values of different shapes in a file,
To iterate over it i cant find any particular solution after this code.
for (list<list<Point>>::iterator it = Point::gnuPoints.begin();
it != Point::gnuPoints.end();
it++)
{
//My assumption is that another For loop would come but could not apply
as I don't know what is available at the first index of gnuPoints list.
}

Answer 1

for (list<list<Point>>::iterator it = Point::gnuPoints.begin();
it != Point::gnuPoints.end();
it++)
{
for (list<Point>::iterator innerIt = it->begin(); innerIt != it->end(); ++innerIt)
}
If you are already on a compiler that supports c++11, this could be simply written as:
for (const auto& container : Point::gnuPoints)
{
for (const auto& item : container)
{
}
}